The present invention relates to a semiconductor processing method, for use in the formation of semiconductor substrates or liquid crystal substrates, and its apparatus; and, more particularly, the invention relates to a semiconductor processing method and its apparatus, which are provided with a function for in situ measurement of foreign particles floating within a processing chamber that serves for performing processes, such as the formation of thin films (film growth) and etching, and which are capable of determining the state of contamination of the processing chamber.
Processes using plasma, such as those performed in an etching apparatus, are widely applied in the manufacture of semiconductor devices and substrates for liquid crystal display apparatuses.
An example of an apparatus using a plasma process is a plasma etching apparatus. In such a plasma etching apparatus, the reaction products produced by the etching reaction with the plasma accumulate on the walls of the plasma processing chamber or the electrodes, and as time passes these accumulated reaction products separate and become floating particles. These floating particles can drop onto the wafer at the instant when the etching process is finished and the plasma discharge is stopped, so as to become adhered particles, resulting in bad circuits and a bad pattern appearance. In the end, these particles become a factor in a low product yield and a reduced reliability of the elements.
A great many apparatuses for detecting foreign particles that have adhered on the wafer surface in the above-mentioned manner have been reported and are being applied, but these apparatuses perform an inspection under conditions where the wafer is removed from the plasma processing apparatus. At that time, when it is determined that most foreign particles will occur, the processing of another wafer is already under way, and a problem results in the form of a reduced yield, because of the large volume of bad wafers that are produced. Also, in the evaluation after the process, the distribution of the occurrence of foreign particles within the processing chamber and the change in conditions over time are not determined.
Consequently, a technique for providing real-time, in situ, monitoring of the state of contamination within a processing chamber is in demand in various technical fields, such as semiconductor manufacture and liquid crystal device manufacture. The size of the particles floating within the processing chamber is in the sub-micron to several hundred micrometer range. In the semiconductor field, where densification is progressing to provision of a 256 Mbit DRAM (dynamic random access memory) and a 1 Gbit DRAM, the minimum line width of a circuit pattern is 0.25 to 0.18 xcexcm and is progressively getting smaller. Thus, the size of the particles to be detected must also be on the order of a sub-micron.
The conventional techniques for monitoring foreign particles floating within a processing chamber (vacuum processing chamber), such as a plasma processing chamber, include the technologies disclosed in Japanese Patent Laid-open Publications No. H3-25355 (publication 1), H10-213539 (publication 2), H11-251252 (publication 3), and H11-330053 (publication 4).
The above-mentioned publication 1 discloses a microscopic particle measurement apparatus for measuring microscopic particles that have adhered on the semiconductor device substrate surface and microscopic particles that are floating using the scattering of a laser beam. This apparatus includes a laser beam phase modulator for generating two laser beams that are modulated with prescribed frequencies so that the wavelengths thereof are the same, but the phases thereof are different; an optical system for causing the two laser beams to intersect in a space including microscopic particles, which represent the measurement subject; a photodetector for receiving light scattered by the microscopic particles in the region where the two laser beams intersect and converting the light to an electrical signal; and a signal processor for extracting a signal component, wherein the phase modulation signal and frequency in the laser beam phase modulator are the same or double in the electrical signal from this scattered light, and the phase difference between the phase modulated signals is constant over time.
The above-mentioned publication 2 makes note of a microparticle sensor that includes a beam emitter for emitting a beam of light so as to radiate the beam across a measured volume; a detector, including a photodetector, and an optical system for focusing the scattered light from the measured volume and directing that light to the photodetector, whereby the photodetector generates a signal representing the intensity of the light directed to the photodetector; and signal processing means having a pulse detector which is connected so as to analyze the signal from the photodetector and detect pulses in the signal from the photodetector, and an event detector for the microparticles, which specifies a series of pulses caused by scattered light resulting from the microparticles following irradiation a plurality of times with the above-mentioned beam during the time when those microparticles are moving within the measured volume.
Publications 3 and 4 make note of foreign particle monitoring technology wherein a beam of light, having a desired wavelength and with its intensity modulated by a desired frequency, is radiated within a processing chamber, scattered light attained from within the processing chamber is separated into the desired wavelength component, and collected and converted to a signal; and by the extraction of the intensity modulated component with the desired frequency from that signal, a signal representing the foreign particles floating in or near the plasma is separated and detected from that signal resulting from the plasma. In particular, FIGS. 15 and 16 in publication 3 show an optical system for detecting side-scattered light, which comprises an interference filter, an imaging lens, an optical length correcting prism, a plurality of pinholes, and a parallel output type photodiode array.
However, in the semiconductor field where densification is progressing to provision of a 256 Mbit DRAM and a 1 Gbit DRAM, the minimum line width of the circuit pattern is 0.25 to 0.18 xcexcm and is progressively getting smaller. Thus, the size of the particles to be detected must also be on the order of a sub-micron.
In the above-mentioned publications 1 and 2, however, the application of the technology is limited to the observation of comparatively large particles, because of the difficulty in separating the particle-scattered light and the plasma emission, and it is believed to be difficult to detect microscopic particles on the order of a sub-micron.
On the other hand, in the above-mentioned publications 3 and 4, the problem is that the detection optical systems are complicated and expensive, even though it is possible to separate the particle-scattered light and the plasma emission. In this regard, a beam of light having the desired wavelength and with its intensity modulated by the desired frequency, is radiated within a processing chamber, and scattered light attained from within the processing chamber is separated into the above-mentioned desired wavelength component, collected and converted to a signal, so that the intensity modulated component with the desired frequency can be extracted from that signal, but the processing is complicated and expensive.
The present invention is directed to a plasma processing method and an apparatus therefor which provide improved yields, and which makes possible real-time monitoring of the state of contamination in a plasma processing chamber with a simplified detecting optical system, and with greatly improved detection sensitivity for detecting and separating the plasma emission for sub-micron, floating microscopic particles in or near the plasma in a plasma processing chamber.
Also, the present invention is directed to a semiconductor processing method which makes it possible to manufacture high-quality semiconductors with high yields, and which makes possible real-time monitoring of the state of contamination in a plasma processing chamber with a simplified detecting optical system, and with greatly improved detection sensitivity for detecting and separating the plasma emission for sub-micron, floating microscopic particles in or near the plasma in a plasma processing chamber.
Specifically, in accordance with the present invention, when the desired thin film growth or finishing process for a processed substrate (semiconductor substrate) is performed in a processing chamber, for example, when a laser beam from an external laser beam source passes through a viewing window and radiates into the processing chamber, light scattered by foreign particles within the processing chamber is then received by one detecting lens, and from the above-mentioned detection signal, the number, size, and distribution of foreign particles, as well as the state of contamination of the inner walls of the processing chamber, are determined, and the results of this determination are displayed on a display.
Also, the present invention is directed to a semiconductor processing method and plasma processing method having an introduction step of introducing a semiconductor substrate into a processing chamber; a plasma generating step of generating plasma in the processing chamber, a processing step of processing a semiconductor substrate by processing the semiconductor substrate by reaction with the generated plasma in the processing chamber: a foreign particle detection step of detecting foreign particles floating in or near the generated plasma in the processing chamber; and a removal step of removing the processed semiconductor substrate from the processing chamber.
The above-mentioned foreign particle detection step includes a radiation step of radiating a laser beam through a window in the processing chamber and causing the beam to scan over and irradiate the semiconductor substrate in the processing chamber, using a scanning optical system; a detecting step wherein, when the laser beam is scanned over the semiconductor substrate in the radiation step, scattered light from floating foreign particles occurring across the entire region over the semiconductor substrate passes through a window in the processing chamber and is focused on the plane of incidence by a detecting lens, which has a wide field angle, so as to cause the light to be incident to the plane of incidence, and a detecting optical axis different from the illuminating optical axis of the scanning optical system, and the light focused on the plane of incidence is received with a detector and is converted to a first signal; and a step of attaining floating foreign particle information from the first signal.
These and other objects, features and advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention, as illustrated in the accompanying drawings.